Compiled & shared by-DR. RAJESH KUMAR SINGH, (LIVESTOCK & POULTRY CONSULTANT), JAMSHEDPUR, JHARKHAND,INDIA 9431309542, rajeshsinghvet@gmail.com
Shell Thickness ——————-
Many labs and companies use the measurement of shell thickness as the only indicator of shell quality. However, the eggshell is a proteoceramic and its functional properties are not necessarily directly related to its thickness. A more resilient shell is one that can absorb and tolerate more impact and other physical forces without cracking. Shell integrity is related to its structure and the pattern in which the calcium minerals are deposited (i.e. crystal size and organization) to form the different layers of the shell. From the breeding standpoint, selecting only for increased shell thickness is not sufficient.
Puncture Score———————————–
Puncture score is a test used to measure the plasticity of the shell. As the test doesn’t damage the integrity of the shell, the Puncture Score can be measured at more than one location on the shell, allowing for better accuracy. Measuring Puncture Score requires special instrumentation and calibration and is not a widely used measurement of shell quality in the industry.
Breaking Strength —————————
Breaking Strength measures the amount of force required to break the shell. It is a pure resistance measurement, and as it is destructive, only one measurement per egg is possible.
Acoustic Resonance————————
A large body of research proves the usefulness of acoustic resonance and its derivate measures, such as the “dynamic stiffness” or dynamic shell strength (Kdyn), in predicting shell quality. The Acoustic Egg Test device developed by the University of Leuven, Belgium provides accurate and repeatable values of acoustic frequency and Kdyn. In addition, the test classifies eggs as “cracked” vs. “normal” and also identifies micro-cracks, which are not visible with the naked human eye. The use of dynamic stiffness to improve shell quality is important in selection of pure line layers. Hy-Line measures large numbers of eggs throughout the production period to ensure selection pressure continues on this important trait.
Shell Color——————————————————————-
Shell color is an important trait to be studied due to different market preferences regarding egg color around the world. While there are a variety of options, Eg. Hy-Line uses an internal shell color index based on the three-parameter (L,a,b) values.
Albumen Height
The albumen height and the adjusted Haugh Unit values (accounting for differences in egg weight) are routinely measured. The albumen height is measured midway between the edge of the yolk and the thick egg white, using an electronic sensor device. Albumen quality is very important in markets where raw egg consumption is customary. Also, Haugh Units are used as a global indicator of egg freshness. Eggs with higher albumens and greater Haugh Unit values can be stored for a longer time while still maintaining their fresh appearance when used by the consumer
Egg and Yolk Weight, Percent Yolk and Egg Solids———–
Total egg and yolk weights are measured using high precision scales. It is well recognized that the yolk, being rich in fat, contains most of the total solids of the egg. Therefore, indirect genetic selection for solids is accomplished by increasing relative yolk size. Dry matter percentage is measured in individual egg samples by separating the egg into its main components – shell plus membranes, yolk and albumen. Each component is weighed and then samples of albumen and yolk are dried. This process is an excellent benchmarking tool to assess and monitor commercial products for the total solid content of their eggs. The formation of the egg is a fascinating part of the chicken’s unique role in feeding the world’s growing appetite for affordable protein and nutrition. Perhaps we take for granted the complicated process to produce a quality egg and the number of factors that affect the quality of the final product. Flock health, management, diet and genetic selection all play an important role in achieving the highest quality product for the egg industry’s customers.
ENSURING GOOD EGG QUALITY————————-
1.Disease Control
Proper disease diagnosis and good vaccination programs are important to minimize the infectious disease incidence in a flock. Infectious Bronchitis and Egg Drop Syndrome have already been mentioned as diseases that can have significant impact on shell quality. Other diseases that could affect shell appearance include Newcastle Disease and Avian Influenza. Stress from any disease can indirectly result in loss of egg quality.
2.Nutrition
Shell strength is determined by the calcium metabolism of the hen which is a dynamic flow of calcium from the feed and bone to the uterus. There is a demand of 2–2.5 grams of calcium per egg produced, almost regardless of egg size. This calcium requirement must be principally supplied by the feed, but the hen may also mobilize calcium from medullary bone reserves to form the eggshell. Medullary bone acts as a readily available reservoir of calcium if required during shell formation. The quantity of calcium contributed to the eggshell from these bone reserves will depend on the rate and quantity of calcium absorbed from the digestive contents during shell deposition. When adequate calcium is supplied by the diet, the bird will replenish and maintain the medullary bone calcium content during periods when no shell formation is occurring. If dietary calcium supply is inadequate, then calcium will be mobilized from cortical bone to meet the required levels for proper shell formation. Continued calcium deficiency will result in the appearance of soft bones and eventually a drop in production, or in acute deficiency, the bird will stop laying. Unless a bird enters into molt and experiences a drop of estrogen levels, the skeletal bone is not replenished with calcium. Shell quality cannot be maintained for long without adequate levels of calcium, phosphorus and Vitamin D in the layer diet. Other micronutrients including Magnesium, Iron, Copper, Manganese, Zinc, Vitamin K and certain amino acids function in calcium transport and bone matrix turnover. Even some B vitamins (Folic acid, Niacin, B12) have been associated with positive effects on shell quality. Dietary electrolyte balance is also an important consideration for shell quality as it can influence the mineralization of the shell. High levels of dietary chloride should generally be avoided. Replacing a proportion of the sodium from salt with sodium from sodium bicarbonate or sodium carbonate sources has been shown to have positive impact on shell quality. Vitamin D is essential for the intestinal absorption of calcium and phosphorus. Phosphorus is present at a low level in the eggshell, but is important for replenishing the medullary bone. So there must be sufficient phosphorous available from the diet to assimilate the calcium into the bone matrix. The mobilization of calcium from bone is inefficient and should be minimized by supplying calcium mostly from dietary sources. Late afternoon feedings, midnight feedings and coarse limestone particle size extend calcium absorption from feed into the night time period. These measures preserve medullary bone and lower the demand for dietary phosphorus.
HEAT STRESS AND SHELL QUALITY —————-
The heat stressed flock often lays eggs with thinner, weaker shells because of acid/base disturbances in the blood as a result of panting (hyperventilation). As the hen pants to lose body heat there is excessive loss of CO2 gas from the blood. Lower CO2 causes blood pH to elevate or become more alkaline. The higher blood pH reduces the amount of ionized calcium and carbonate delivered to the uterus for eggshell formation. Increasing the amount of calcium in the feed does not correct this problem. Reduced feed intake under heat stress conditions also contributes to thin eggshells. The dietary electrolyte balance can also play a role in shell quality, particularly during periods of heat stress. The concentration of chloride in the diet should be carefully balanced in relation to sodium and potassium and even reduced during hot periods. Some additional benefits may be expected with the use of bicarbonate sources.
